Monday, February 01, 2010

Revit and the 2 Mile Limit

I’ve read a few posts on this subject in the last few months, a couple more recently offering a way to get around the issue. I echoed a post at the Revit Clinic blog a few months ago too. Paying homage to “The Princess Bride” movie I dubbed the files affected by this issue “Files of Unusual Size” or FOUS, like the “Rodents of Unusual Size”, ROUS.

Revit examines the cad file you want to import and determines how “big” the data is. If it finds that all the data in the file results in data greater than two miles across, either horizontally or vertically it will generate the error message. It is not just that survey data is a great distance from the origin in the file. The survey itself might be fine but there is some geometry lurking a great distance from the important stuff that creates the condition that Revit is hoping to avoid.

You can test this out yourself. Create a little survey of lines and then park a line more than two miles away from those lines. It could be as simple as two lines very far apart. Import the file and Revit complains.

There are a few ways to resolve this. You can fix the file or just fool Revit into accepting the large data despite its best effort to do otherwise. The correct way should be the solution that is the least work and hopefully doesn’t put you at risk for altering the civil file in a way that leaves room for error.

To fix the file you can refer to the earlier post here or to the one at The Revit Clinic. If you are interested in fooling Revit and doing “nothing” to the file then consider this post.

Another solution that I’ve used several times is to create a new empty cad file (container file) and then create a new external reference with the FOUS in this new container file. Use the same 0,0,0 world coordinate location and make sure the external reference is attached. Now import this container file with its attached external reference, no warning message, the size of the FOUS is “hidden” by the container. Happy Imports!

No comments: